Generally, a chip resistor includes a rectangular parallelepiped insulating substrate, a pair of front electrodes, a resistive element, an insulating protective layer, a pair of back electrodes, a pair of end-surface electrodes, and a pair of external electrodes. The insulating substrate is made of ceramics. The pair of front electrodes are disposed on a front surface of the insulating substrate so as to be opposite to each other with interposition of a predetermined interval therebetween. The resistive element is provided on the front surface of the insulating substrate so as to be connected to the pair of front electrodes. The protective layer is provided so as to cover the resistive element. The pair of back electrodes are disposed on a back surface of the insulating substrate so as to be opposite to each other with interposition of a predetermined interval therebetween. The pair of end-surface electrodes are provided on opposite end surfaces of the insulating substrate so as to establish electrical continuity between the front electrodes and the back electrodes respectively. The pair of external electrodes are formed by plating treatment on outer surfaces of the end-surface electrodes.
The chip resistor configured thus is surface-mounted on a circuit board in the following manner. That is, after a solder paste is printed on lands provided on the circuit board, the external electrodes of the chip resistor are mounted on the lands with the back electrodes down. In this state, the solder paste is melted and solidified. Thus, the chip resistor is surface-mounted on the circuit board. On this occasion, no problem arises when the chip resistor assumes a posture at which the back surface of the insulating substrate faces down. When the chip resistor assumes another posture at which one of side surfaces of the insulating substrate on which no electrode is present faces down, it is however difficult to bring the electrodes into tight contact with the solder paste on the lands to thereby result in shortage of solder connection strength (fixability). Therefore, the chip resistor in which no electrode is formed on each of the side surfaces of the insulating substrate is not suitable for bulk mounting.
As a background-art example of a chip resistor adapted for bulk mounting, the following technique has been known, as described in PTL 1. That is, in a producing process for obtaining a large number of individual chip element assemblies from a large-sized substrate, the large-sized substrate is primarily broken along primary division grooves to thereby obtain strip-shaped substrates. Then, a silver paste is applied onto end surfaces of the strip-shaped substrates to form end-surface electrodes. During that time, the silver paste is not only applied onto the end surfaces but also made to flow into secondary division grooves. Then, the strip-shaped substrates are secondarily broken along the secondary division grooves so as to be separated into the individual chip element assemblies. In each of chip resistors produced thus, side-surface electrodes connected to the end-surface electrodes are also formed on the side surfaces of the chip element assembly which are secondary break surfaces, and electrodes are present on four surfaces including the front and back of a rectangular parallelepiped insulating substrate. Accordingly, the chip resistor can be mounted at a posture having any of the four surfaces (an upper surface, a lower surface and the opposite side surfaces) on a circuit board.
In addition, as another background-art example of the chip resistor adapted for bulk mounting, the following configuration has been known, as described in PTL 2. That is, two ceramics substrates are bonded to each other to forma chip element assembly shaped like a rectangular cylinder. A resistive element and a pair of internal electrodes are provided between the ceramics substrates. Moreover, cap-shaped end-surface electrodes are provided on lengthwise opposite end portions of the chip element assembly. The end-surface electrodes are connected to the internal electrodes which are exposed from lengthwise opposite end surfaces of the ceramics substrates. According to the chip resistor configured thus, the cap-shaped end-surface electrodes extend to an upper surface, a lower surface and opposite side surfaces of the chip element assembly, and the chip element assembly has an external shape like a rectangular cylinder having the same dimensions on each of the four surfaces. Accordingly, the chip resistor can be mounted at a posture having any of the four surfaces (the upper surface, the lower surface and the opposite side surfaces) on the circuit board.